An outstanding challenge in the field of quantum information science is the ability to connect multiple quantum processors or sensors in a quantum network. This capability will enable distributed quantum computation and sensing, as well as secure long distance communication based on networked quantum repeaters, each containing an interface between stationary and flying qubits, quantum memory, and processing capability. Moreover, at any stage of the development of quantum computers, there may be a practical limitation on the achievable number of qubits in a single processing unit. Therefore, quantum networks will enable a route towards building a large scale quantum processor based on a modular architecture[1]}.
